A walk behind earth working apparatus penetrates and/or moves earth during operation thereof while a user walks behind the apparatus or follows behind the apparatus on a chariot type attachment. A walk behind earth moving apparatus includes, for example, a walk behind soil aerator. Several different types of soil aerators with rotating tines are known. On all these aerators, the tines are mounted on shafts for rotation about an axis, and, as each tine rotates, it pierces the ground and pulls up a plug of soil.
The fact that the aerator tines dig into the soil makes aerators much more difficult to maneuver than a typical piece of lawn equipment, like a lawn mower, which remains entirely on top of the ground, because the tines that are sticking into the ground limit the ability of the aerator to move along the ground. As a result, aerators generally travel in a straight line, have a very large turning radius and are very difficult to handle. Each type of aerator uses a somewhat different mechanism for reducing the interference of the tines when making a turn.
First, there are aerators that are pulled behind a tractor. The tines on these aerators are not driven. They simply free-wheel about a shaft as the aerator frame is pulled along by the tractor. These aerators typically include several different tine assemblies mounted for freewheeling about a single shaft. These aerators can make wide turns, with the individual tine assemblies free-wheeling at varying speeds to accommodate the turning aerator as the tractor pulls the aerator along. There still may be some resistance and some dragging of tines that are inserted into the soil as the aerator is pulled around a curve, which can tear up turf and is undesirable, but, if a large enough radius of curvature is used, the result is generally acceptable.
Next, there are walk-behind aerators, which include a frame with an internal combustion engine which typically uses a belt drive (or drives) to drive the tine assemblies. The driven tines dig into the soil and propel the aerator forward along the ground as they rotate, with the human operator walking behind the aerator to steer it and control it. Some of these aerators can be driven around curves if a large radius of curvature is used, particularly if they use a differential to enable the outer tines to rotate at a faster speed than the inner tines while the tine assemblies are being driven. However, they rely on the use of a clutch to disengage the drive to the aerator tines so the tine assemblies become freewheeling in order to reduce the amount of interference from the tines when the operator wants to make a tight turn or wants to pull the aerator backwards.
Finally, there are large, riding aerators, on which the operator stands or sits. These riding aerators typically have separate, left and right hydrostatic drives, which separately drive left and right sets of tine assemblies. The operator may speed up one set of rotating tines and slow down another to make a wide turn. To make sharp turns, the operator stops the aerator, raises the tines out of the ground to get them completely out of the way, then drives the aerator to the desired position, then stops and lowers the tines back into the ground and then begins driving the tines again.
So, as explained above, all the aerators rely on some mechanism to get the tines out of the way in order to be able to make tight turns or other difficult maneuvers—either allowing the tine assemblies to freewheel or raising the tine assemblies entirely out of the ground during the difficult maneuver.
The aerator described by Kinkead in U.S. Pat. No. 6,708,773 is an example of a walk-behind aerator which uses a belt drive with a clutch mechanism that allows the operator to disengage the drive and allow the tines to freewheel during difficult maneuvers. It additionally facilitates turning by driving the left and right sets of tines through a differential, and through the use of left side and right side individual brakes, to manually overcome the resistance associated with making wide turns while the tines are in the ground, as described below. However, this arrangement is still very difficult for the operator to maneuver.
If the operator wants to make a large radius turn, he either pulls back on the handle on one side of the aerator or uses a brake to slow down the tines on one side of the aerator while pushing on the other side to direct the aerator into the turn. Due to the way a differential works, when the inner set of tines is moving very slowly or is stationary, the outer set of tines rotates at twice the normal speed, so the operator often finds himself running to keep up with the aerator as it makes the wide turn.
If the operator wants to make a tight turn, he disengages the clutch to make the tines freewheeling to minimize their interference with the maneuver, and then he pushes the aerator manually around the tight turn. After completing the tight turn, he re-engages the clutch, which causes the aerator to jerk forward as the tines begin driving again.
If the operator wants to back up this walk-behind aerator, he again disengages the clutch to make the tines freewheeling, and he then manually pulls the aerator backwards. This can require a substantial amount of human strength, especially if it involves pulling the aerator uphill, which even may be impossible in some situations.